We learn that depths provided sufficient evidence to figure the chi and psi wheel patterns – which were changing quarterly or monthly, only. And , we know that before the machine age of GCCS really got going that this change pattern was amenable to hand methods of cryptanalysis.
We also learn that the machine wheel was viewed, in the original design concept, as the daily wheel (to be changed much as in the enigma world). What is interesting is the reference to cribs, as a valid means to assist with wheel breaking (assuming that countermeasures didn’t make crib matching too hard).
fascinating to see related the chain of assumptions and deductions – that would reveal a crypto tell.